Oral recombinant methioninase increases TRAIL receptor-2 expression to regress pancreatic cancer in combination with agonist tigatuzumab in an orthotopic mouse model

The potential of methioninase for cancer treatment

Cancer cells are addicted to L-methionine (L-Met) and have a much greater requirement for L-Met than normal cells due to excess transmethylation, termed the Hoffman effect. By targeting this vulnerability through dietary restriction of L-Met, researchers have been able to achieve promising results in inhibiting tumor growth and eradicating cancer cells. Methioninase (EC 4.4.1.11; METase) catalyzes the transformation of L-Met into α-ketobutyrate, ammonia, and methanethiol. The use of METase was initially limited due to its poor stability in vivo, high immunogenicity, and enzyme-induced inactivating antibodies. These issues could be partially resolved by PEGylation, encapsulation in erythrocytes, and various site-directed mutagenesis. The big breakthrough came when it was discovered that METase is effectively administered orally. The enzyme L-asparaginase is approved by the FDA for treatment of acute lymphoblastic leukemia. METase has more potential as a therapeutic since addiction to L-Met is a general and fundamental hallmark of cancer.

Targeting methionine metabolism in cancer: opportunities and challenges

Reprogramming of methionine metabolism is a conserved hallmark of tumorigenesis. Recent studies have revealed mechanisms regulating methionine metabolism within the tumor microenvironment (TME) that drive both cancer development and antitumor immunity evasion. In this review article we summarize advancements in our understanding of tumor regulation of methionine metabolism and therapies in development that target tumor methionine metabolism. We also delineate the challenges of methionine blockade therapies in cancer and discuss emerging strategies to address them.

Significance of TRAIL/Apo-2 ligand and its death receptors in apoptosis and necroptosis signalling: Implications for cancer-targeted therapeutics

The human immune defensesystem routinely expresses the tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), which is the most prevalent element for antitumor immunity. TRAIL associates with its death receptors (DRs), DR4 (TRAIL-R1), and DR5 (TRAIL-R2), in cancer cells to initiate the intracellular apoptosis cascade. Accordingly, numerous academic institutions and pharmaceutical companies havetried to exploreTRAIL's capacity to kill tumourcells by producing recombinant versions of it (rhTRAIL) or TRAIL receptor agonists (TRAs) [monoclonal antibody (mAb), synthetic and natural compounds, etc.] and molecules that sensitize TRAIL signalling pathway for therapeutic applications. Recently, several microRNAs (miRs) have been found to activate or inhibit death receptor signalling. Therefore, pharmacological regulation of these miRs may activate or resensitize the TRAIL DRs signal, and this is a novel approach for developing anticancer therapeutics. In this article, we will discuss TRAIL and its receptors and molecular pathways by which it induces various cell death events. We will unravel potential innovative applications of TRAIL-based therapeutics, and other investigated therapeutics targeting TRAIL-DRs and summarize the current preclinical pharmacological studies and clinical trials. Moreover, we will also emphasizea few situations where future efforts may be addressed to modulate the TRAIL signalling pathway.

Increased Response to Immune Checkpoint Inhibitors with Dietary Methionine Restriction in a Colorectal Cancer Model

Dietary methionine restriction (MR), defined as a reduction of methionine intake by around 80%, has been shown to reproducibly decrease tumor growth and synergize with cancer therapies. In this study, we combined DMR with immune checkpoint inhibitors (ICIs) in a model of colon adenocarcinoma. In vitro, we observed that MR increased the expression of MHC-I and PD-L1 in both mouse and human colorectal cancer cells. We also saw an increase in the gene expression of STING, a known inducer of type I interferon signaling. Inhibition of the cGAS-STING pathway, pharmacologically or with siRNA, blunted the increase in MHC-I and PD-L1 surface and gene expression following MR. This indicated that the cGAS-STING pathway, and interferon in general, played a role in the immune response to MR. We then combined dietary MR with ICIs targeting CTLA-4 and PD-1 in an MC38 colorectal cancer tumor model developed in immunocompetent C57BL/6 mice. The combination treatment was five times more effective at reducing the tumor size than ICIs alone in male mice. We noted sex differences in the response to dietary MR, with males showing a greater response than females. Finally, we observed an increase in membrane staining for the PD-L1 protein in MC38 tumors from animals who were fed an MR diet. MHC-I was highly expressed in all tumors and showed no expression difference when comparing tumors from control and MR-treated mice. These results indicated that MR increased PD-L1 expression both in vitro and in vivo and improved the response to ICIs in mice.

Dietary Manipulation of Amino Acids for Cancer Therapy

Cancer cells cannot proliferate and survive unless they obtain sufficient levels of the 20 proteinogenic amino acids (AAs). Unlike normal cells, cancer cells have genetic and metabolic alterations that may limit their capacity to obtain adequate levels of the 20 AAs in challenging metabolic environments. However, since normal diets provide all AAs at relatively constant levels and ratios, these potentially lethal genetic and metabolic defects are eventually harmless to cancer cells. If we temporarily replace the normal diet of cancer patients with artificial diets in which the levels of specific AAs are manipulated, cancer cells may be unable to proliferate and survive. This article reviews in vivo studies that have evaluated the antitumor activity of diets restricted in or supplemented with the 20 proteinogenic AAs, individually and in combination. It also reviews our recent studies that show that manipulating the levels of several AAs simultaneously can lead to marked survival improvements in mice with metastatic cancers.

Colon-cancer liver metastasis is effectively targeted by recombinant methioninase (rMETase) in an orthotopic mouse model

BACKGROUND

Colorectal cancer liver metastasis (CCLM) is the most frequent cause of death of colorectal cancer. Development of novel new effective therapy is needed for CCLM patients to improve outcome. The aim of the present study was to investigate the efficacy of recombinant methioninase (rMETase) on a CCLM orthotopic mouse model of liver metastasis established using the human colon cancer cell line HT29 expressing red fluorescent protein (RFP).

MATERIALS AND METHODS

Orthotopic CCLM nude mouse models were randomized into two groups: control group (n = 6, PBS 200 µl, i.p., daily); rMETase group (n = 6, 100 units/200 µl, i.p., daily). Tumor volume was measured on day 0 and day 15. Body weight was measured twice a week. All mice were sacrificed on day 15.

RESULTS

rMETase significantly inhibited the increase of the liver metastasis as determined by RFP fluorescence area and intensity (p = 0.016 and 0.015, respectively). There was no significant difference of body weight between either group on any day.

CONCLUSIONS

The present study suggests that rMETase has future potential therapy for CCLM in the clinic.

Increased response to immune checkpoint inhibitors with dietary methionine restriction

Dietary methionine restriction, defined as reduction of methionine intake by around 80%, reproducibly decreases tumor growth and synergizes with cancer therapies. Here, we combined dietary methionine restriction with immune checkpoint inhibitors in a model of colon adenocarcinoma. In vitro , we observed that methionine restriction increased the expression of MHC-I and PD-L1 in both mouse and human colorectal cancer cells. We also saw an increase in the gene expression of STING, a known inducer of type I interferon signaling. Inhibition of the cGAS-STING pathway, pharmacologically or with siRNA, blunted the increase in MHC-I and PD-L1 surface and gene expression following methionine restriction. PD-L1 expression was also This indicated that the cGAS-STING pathway in particular, and interferon in general, is playing a role in the immune response to methionine restriction. We then combined dietary methionine restriction with immune checkpoint inhibitors targeted against CTLA-4 and PD-1 in a MC38 colorectal cancer tumor model in C57BL/6 mice. The combination treatment was five times more effective at reducing tumor size than immune checkpoint inhibition alone in males. We noted sex differences in the response to dietary methionine restriction for the MC38 tumor model in C57BL/6 mice. Finally, we observed an increase in PD-L1 protein expression in MC38 tumors from animals who were fed a methionine-restricted diet. Furthermore, the distribution of CD8 staining changed from mostly peripheric in the controls, to intratumoral in the methionine-restricted tumors. MHC-I, which has a high basal expression in MC38 cells, was highly expressed in all tumors. These results indicate that methionine restriction improves the response to immune checkpoint inhibitors in mice, and that this improvement is associated with the cGAS-STING pathway and interferon signaling.

Synergy of oral recombinant methioninase (rMETase) and 5-fluorouracil on poorly differentiated gastric cancer

Gastric cancer is highly malignant and recalcitrant to first line chemotherapies that include 5-fluorouracil (5-FU). Cancer cells are addicted to methionine for their proliferation and survival. Methionine addiction of cancer is known as the Hoffman effect. Methionine restriction with recombinant methioninase (rMETase) has been shown to selectively starve cancer cells and has shown synergy with cytotoxic chemotherapy including 5-FU. The present study aimed to investigate the efficacy of rMETase alone and the combination with 5-FU on poorly differentiated human gastric cancer cell lines (MKN45, NUGC3, and NUGC4) in vitro and vivo. rMETase suppressed the tumor growth of 3 kinds of poorly differentiated gastric cancer cells in vitro. The fluorescence ubiquitination-based cell cycle indicator (FUCCI) demonstrated cancer cells treated with rMETase were selectively trapped in the S/G₂ phase of the cell cycle. In the present study, subcutaneous MKN45 gastric cancer models were randomized into four groups when the tumor volume reached 100 mm³: G1: untreated control; G2: 5-FU (i.p., 50 mg/kg, weekly, three weeks); G3: oral-rMETase (o-rMETase) (p.o., 100 units/body, daily, three weeks); G4: 5-FU with o-rMETase (5-FU; i.p., 50 mg/kg, weekly, three weeks o-rMETase; p.o., 100 units/body, daily, three weeks). All mice were sacrificed on day 22. Body weight and estimated tumor volume were measured twice a week. 5-FU and o-rMETase suppressed tumor growth as monotherapies on day 18 (p = 0.044 and p = 0.044). However, 5-FU combined with o-rMETase was significantly superior to each monotherapy (p < 0.001 and p < 0.001, respectively) and induced extensive necrosis compared to other groups. The combination of 5-FU and o-rMETase shows promise for transformative therapy for poorly differentiated gastric cancer in the clinic.

Oral Installation of Recombinant Methioninase-producing Escherichia coli into the Microbiome Inhibits Colon-cancer Growth in a Syngeneic Mouse Model

BACKGROUND/AIM

All cancer types so far tested are methionine-addicted. Targeting the methionine addiction of cancer with recombinant methioninase (rMETase) has shown great progress in vitro, in mouse models, and in the clinic. However, administration of rMETase requires multiple doses per day. In the present study, we determined if rMETase-producing Escherichia coli JM109 (E. coli JM109-rMETase) might be an effective anticancer agent when installed into the microbiome.

MATERIALS AND METHODS

E. coli JM109-rMETase was administered to a syngeneic model of MC38 colon cancer growing subcutaneously in C57BL/6 mice. JM109-rMETase was administered orally by gavage to the mice twice per day. Tumor size was measured with calipers.

RESULTS

The administration of E. coli JM109-rMETase twice a day significantly inhibited MC38 colon-cancer growth. E. coli JM109-rMETase was found in the stool of treated mice, indicating it had entered the microbiome.

CONCLUSION

The present study indicates the potential of microbiome-based treatment of cancer targeting methionine addiction.

Screening, characterization and anti-cancer application of purified intracellular MGL

L-methionine-γ-lyase (MGL) producing bacterial isolates were screened from soil samples that further characterized as 'Klebsiella oxytoca BLM-1' by biochemical and 16S rDNA sequencing. Intracellular MGL obtained from K. oxytoca BLM-1 by sonication was purified by Octyl-Sepharose and Sephadex G-200 column chromatography. MALDI-TOF-MS analysis of protein band (Mr ~ 63 kDa) confirmed the PLP-dependence and structural similarity with MGL enzyme. Purified MGL (1.1 μg) exhibited the maximum activity in potassium phosphate buffer (80 mM; with L-met 20 mM pH 7.0) at 37 °C. That further enhanced in the presence of NaCl (2 mM), Tween-80 (1.0 %; v/v) and EDTA (5 mM). K_m and V_max for purified MGL by using L-met as substrate was found to be 5.32 mM and 0.386 U/mL/min. The purified MGL showed PLP dependence and the half-life was 365.59 min. The MGL was effective against breast cancer (MCF7), gastric adenocarcinoma and human glioblastoma (U87MG) cancer cell lines with IC₅₀ values of purified MGL 0.041 U/mL, 0.008 U/mL and 0.009 U/mL, respectively. The U87MG, greatly affected by MGL treatment, when cultured in DMEM medium (10 mL) with PLP, homocysteine and 10 % FCS as compared to control/untransformed mouse spleen cells.

Linkage of methionine addiction, histone lysine hypermethylation, and malignancy

Methionine addiction, found in all types of cancer investigated, is because of the overuse of methionine by cancer cells for excess transmethylation reactions. In the present study, we compared the histone H3 lysine-methylation status and degree of malignancy between methionine-addicted cancer cells and their isogenic methionine-independent revertants, selected by their growth in low concentration of methionine. The methionine-independent revertans can grow on low levels of methionine or independently of exogenous methionine using methionine precursors, as do normal cells. In the methionine-independent revertants, the excess levels of trimethylated histone H3 lysine marks found in the methionine-addicted parental cancer cells were reduced or lost, and their tumorigenicity and experimental metastatic potential in nude mice were also highly reduced. Methionine addiction of cancer is linked with malignancy and hypermethylation of histone H3 lysines. The results of the present study thus provide a unique framework to further understand a fundamental basis of malignancy.

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Methionine(MET)-independent revertants were selected from MET-addicted cancer cells

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MET-independent revertants had greatly reduced malignancy

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MET-independent revertants have lost or reduced methylation of H3 lysine marks

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MET addiction, malignancy, and hypermethylated H3 lysine marks are linked

Mesenchymal Stem/Stromal Cell-Based Delivery: A Rapidly Evolving Strategy for Cancer Therapy

Mesenchymal stem/stromal cell (MSC)-based therapy has become an attractive and advanced scientific research area in the context of cancer therapy. This interest is closely linked to the MSC-marked tropism for tumors, suggesting them as a rational and effective vehicle for drug delivery for both hematological and solid malignancies. Nonetheless, the therapeutic application of the MSCs in human tumors is still controversial because of the induction of several signaling pathways largely contributing to tumor progression and metastasis. In spite of some evidence supporting that MSCs may sustain cancer pathogenesis, increasing proofs have indicated the suppressive influences of MSCs on tumor cells. During the last years, a myriad of preclinical and some clinical studies have been carried out or are ongoing to address the safety and efficacy of the MSC-based delivery of therapeutic agents in diverse types of malignancies. A large number of studies have focused on the MSC application as delivery vehicles for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), chemotherapeutic drug such as gemcitabine (GCB), paclitaxel (PTX), and doxorubicin (DOX), prodrugs such as 5-fluorocytosine (5-FC) and ganciclovir (GCV), and immune cell-activating cytokines along with oncolytic virus. In the current review, we evaluate the latest findings rendering the potential of MSCs to be employed as potent gene/drug delivery vehicle for inducing tumor regression with a special focus on the in vivo reports performed during the last two decades.

Metabolic Reprogramming in Anticancer Drug Resistance: A Focus on Amino Acids

Overcoming anticancer drug resistance is a major challenge in cancer therapy, requiring innovative strategies that consider the extensive tumor heterogeneity and adaptability. We provide recent evidence highlighting the key role of amino acid (AA) metabolic reprogramming in cancer cells and the supportive microenvironment in driving resistance to anticancer therapies. AAs sustain the acquisition of anticancer resistance by providing essential building blocks for biosynthetic pathways and for maintaining a balanced redox status, and modulating the epigenetic profile of both malignant and non-malignant cells. In addition, AAs support the reduced intrinsic susceptibility of cancer stem cells to antineoplastic therapies. These findings shed new light on the possibility of targeting nonresponding tumors by modulating AA availability through pharmacological or dietary interventions.

Methionine dependence in tumor cells: The potential role of cobalamin and MMACHC

Methionine dependence of tumor cell lines, the inability to grow in tissue culture media lacking methionine but supplemented with homocysteine, has been known for decades, but an understanding of the mechanism underlying this phenomenon remains incomplete. Methionine dependence of certain glioma and melanoma cell lines has been linked to alterations in the metabolism of cobalamin (vitamin B₁₂). In the MeWo LC1 melanoma line, complementation analysis demonstrated that the genetic defect affected the same locus mutated in the cblC inborn error of cobalamin metabolism; hypermethylation of the MMACHC promoter was subsequently demonstrated. Analysis of data in the Cancer Cell Line Encyclopedia showed increased MMACHC methylation levels in melanoma lines compared to other types of cancer. RNA sequencing data from isolated tumors, tabulated at the cBioPortal for Cancer Genomics website, showed decreased MMACHC expression compared to other tumors; and methylation data tabulated at the TGGA Wanderer website demonstrated increased MMACHC methylation. These data suggest that disruptions in cobalamin metabolism might play a more general role in methionine dependence, and potentially in the pathogenesis of melanoma cell lines and primary tumors.

Choline kinase alpha impairment overcomes TRAIL resistance in ovarian cancer cells

Background

Choline kinase-α (ChoKα/CHKA) overexpression and hyper-activation sustain altered choline metabolism conferring the cholinic phenotype to epithelial ovarian cancer (OC), the most lethal gynecological tumor. We previously proved that CHKA down-modulation reduced OC cell aggressiveness and increased sensitivity to in vitro chemotherapeutics’ treatment also affecting intracellular content of one-carbon metabolites. In tumor types other than ovary, methionine decrease was shown to increase sensitivity to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)-receptor 2 triggering. These effects were suggestive of a potential role for ChoKα in regulating susceptibility to TRAIL cytokine.

Methods

The relationship between ChoKα/CHKA and TRAIL-receptor 2 (TRAIL-R2) expression was investigated in silico in OC patients’ GEO datasets and in vitro in a panel of OC cell lines upon transient CHKA silencing (siCHKA). The effect of siCHKA on metabolites content was assessed by LC-MS. The triggered apoptotic signalling was studied following soluble-TRAIL or anti-TRAIL-R2 agonist antibody treatment. Lipid rafts were isolated by Triton X-100 fractionation. Preclinical ex vivo studies were performed in OC cells derived from patients’ ascites using autologous PBLs as effectors and a bispecific anti-TRAIL-R2/anti-CD3 antibody as triggering agent.

Results

Here we demonstrate that siCHKA specifically overcomes resistance to TRAIL-mediated apoptosis in OC cells. Upon siCHKA we detected: a significant sensitization to caspase-dependent apoptosis triggered by both soluble TRAIL and anti-TRAIL-R2 agonist antibody, a specific increase of TRAIL-R2 expression and TRAIL-R2 relocation into lipid rafts. In siCHKA-OC cells the acquired TRAIL sensitivity was completely reverted upon recovery of ChoKα expression but, at variance of other tumor cell types, TRAIL sensitivity was not efficiently phenocopied by methionine deprivation. Of note, we were also able to show that siCHKA sensitized tumor cells derived ex vivo from OC patients’ ascites to the cytotoxic activity of autologous lymphocytes redirected by a bispecific anti-TRAIL-R2/anti-CD3 antibody.

Conclusions

Our findings suggest that ChoKα/CHKA impairment, by restoring drug-induced or receptor-mediated cell death, could be a suitable therapeutic strategy to be used in combination with chemotherapeutics or immunomodulators to improve OC patients’ outcome.

Histone methylation status of H3K4me3 and H3K9me3 under methionine restriction is unstable in methionine-addicted cancer cells, but stable in normal cells

Methionine addiction is a fundamental and general hallmark of cancer. Methionine addiction prevents cancer cells, but not normal cells from proliferation under methionine restriction (MR). Previous studies reported that MR altered the histone methylation levels in methionine-addicted cancer cells. However, no study has yet compared the status of histone methylation status, under MR, between cancer cells and normal cells. In the present study, we compared the histone methylation status between cancer cells and normal fibroblasts of H3K4me3 and H3K9me3, using recombinant methioninase (rMETase) to effect MR. Human lung and colon cancer cell lines and human normal foreskin fibroblasts were cultured in control medium or medium with rMETase. The viability of foreskin fibroblasts was approximately 10 times more resistant to rMETase than the cancer cells in vitro. Proliferation only of the cancer cells ceased under MR. The histone methylation status of H3K4me3 and H3K9me3 under MR was evaluated by immunoblotting. The levels of the H3K4me3 and H3K9me3 were strongly decreased by MR in the cancer cells. In contrast, the levels of H3K4me3 and H3K9me3 were not altered by MR in normal fibroblasts. The present results suggest that histone methylation status of H3K4me3 and H3K9me3 under MR was unstable in cancer cells but stable in normal cells and the instability of histone methylation status under MR may determine the high methionine dependency of cancer cells to survive and proliferate.